Researchers have found that prisoners considered the highest security risks were less stressed and less violent after watching videos with nature scenes than those who did not. Ecologist Nalini Nadkarni at the University of Utah in Salt Lake City published the study’s findings on September 1, 2017 in the academic journal Frontiers in Ecology and the Environment.

The experiment built on past research that has shown prisoners’ physical and mental health can be improved by regularly seeing plants. “I thought, wow, if we could just calm them with nature rather than with Kevlar vests and riot gear, that would be really great,” Nadkarni said of her 2010 idea for the study. But it took years to find a prison willing to let her test her hypothesis.

According to Nature.com, Nadkarni’s team divided prisoners serving time in solitary at the Snake River Correctional Institution in Ontario, Oregon into two groups of 24. Those in one group could choose to exercise or, up to five times per week, watch 45-minute-long videos showing natural scenes such as mountains, forests and oceans. Those in the other group were offered exercise but no videos. The researchers found that prisoners who had access to the videos reported feeling calmer and were involved in 26% fewer violent incidents.

Nadkarni said her research helped prisoners even if it didn’t dramatically reform the prison system. “As an ecologist, it is not in my power to change the system of mass incarceration,” she stated. “One thing I can do is think about ways that bring the therapeutic value of nature to people who are incarcerated.”